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Meet Grotifer: a CubeSat that Will Provide Highly Accurate Three-Component Electric Field Measurements throughout the Heliosphere
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  • Solène Lejosne,
  • David Auslander,
  • John Bonnell,
  • David Klumpar,
  • Jeremy McCauley,
  • Rubin Meuchel,
  • Forrest Mozer,
  • David Pankow,
  • John Sample,
  • Larry Springer
Solène Lejosne
Space Sciences Laboratory, University Of California, Berkeley

Corresponding Author:solene@berkeley.edu

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David Auslander
Mechanical Engineering Department
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John Bonnell
Space Sciences Laboratory, University Of California, Berkeley
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David Klumpar
Space Science and Engineering Laboratory, Department of Physics, Montana State University - Bozeman
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Jeremy McCauley
Space Sciences Laboratory, University Of California, Berkeley
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Rubin Meuchel
Space Science and Engineering Laboratory, Department of Physics, Montana State University - Bozeman
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Forrest Mozer
Space Sciences Laboratory, University Of California, Berkeley
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David Pankow
Space Sciences Laboratory, University Of California, Berkeley
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John Sample
Space Science and Engineering Laboratory, Department of Physics, Montana State University - Bozeman
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Larry Springer
Space Science and Engineering Laboratory, Department of Physics, Montana State University - Bozeman
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Abstract

No existing instrument is capable of consistently measuring all three components of the DC and low frequency electric field (E-field) throughout the heliosphere with sufficient accuracy to determine the smallest, and most geophysically relevant component: the E-field component parallel to the background magnetic field. E-field measurements in the heliosphere are usually made on spinning spacecraft equipped with two disparate types of double probe antennas: (1) long wire booms in the spin plane, and (2) ~10 times shorter rigid booms along the spin axis. On such systems, the potential difference (signal + noise) is divided by the boom length to produce a resultant E-field component. Because the spacecraft-associated errors are larger nearer the spacecraft, the spin plane components of the E-field are well measured while the spin axis component are poorly measured. As a result, uncertainty in the parallel E-field is usually greater than its measured value. Grotifer leverages more than fifty years of expertise in delivering highly accurate spin plane E-field measurements, while overcoming inaccuracies generated by spin axis E-field measurements. Its design consists of mounting detectors on two rotating plates, oriented at 90° with respect to each other, on a non-rotating central body. Each rotating plate has two component measurements of the E-field such that the Twin Orthogonal Rotating Platforms (TORPs) provide four instantaneous measurements of the E-field, and the three E-field components are well-measured by the rotating detectors. Grotifer (Giant rotifer) is a reference to the rotifer, also known as the “wheel animalcule”, which has twin crowns of antenna-like cilia that appear to rotate in all directions. Grotifer marks a profound change in E-field instrument design that represents the best path forward to close the observational gap that currently hampers resolution of significant science questions at the forefront of space plasma physics research. Here, we present the Grotifer design concept implemented as a 27-U CubeSat, discuss the important features in the design and operation of Grotifer, and demonstrate the feasibility of implementing Grotifer using existing sub-systems and technologies.